A man who confessed to helping strangle his girlfriend apologized to her brother in court today, triggering the latest foul mouthed eruption at the trial of accused Boston mob boss James "Whitey" Bulger.

Stephen "The Rifleman" Flemmi, once a top lieutenant to Bulger, admitted last week bringing his girlfriend Debbie Davis to a house where he claims Bulger leaped out and strangled her.

His apology today, however, wasn't for helping to kill her, or for wrapping her in a tarp and burying her in a shallow grave.

Flemmi, who is serving a life sentence, said he was sorry for mistakenly telling the court that Davis' brother Steve was a "drug dealer."

Flemmi, 79, said he had confused Steve Davis with his brother Mickey, who was killed at Walpole State Prison.

"You're a f***ing liar," Steve Davis barked after leaping to his feet in the crowded South Boston federal court.

Bulger, 83, has traded curses with several witnesses over the five weeks of testimony, including with Flemmi last week.

Bulger, the inspiration for the movie "The Departed," is on trial for a long list of felonies, including 19 murders.

While Bulger's defense has boasted in the opening statement that he made "millions upon millions upon millions" of dollars running his Winter Hill Gang with the help of dirty FBI agents, he has denied killing Debbie Davis.

Flemmi testified that Bulger insisted Debbie Davis be killed because she was aware of his connection to corrupt FBI agent John Connolly.

When the trial resumed this morning, there was still no word on what caused the death of Stephen Rakes, 59, a potential witness against Bulger who was found dead last week at the side of the road in suburban Lincoln, Mass.

Rakes was found with no phone, keys or wallet and his car was nowhere near the scene. Family and friends of Rakes believe the man's body was dumped where he was found.

"He never struck me as the type of person who would consider suicide and certainly not in the midst of this case, which he's waited for years to see through," Rakes' lawyer, Paul V. Kelly, a former federal prosecutor, told ABC News. "Everything smacks of something suspicious. And what the hell was he doing walking in the woods in the middle of nowhere in Lincoln, Mass.?"

Kelly said authorities found no suicide note.

Results of an autopsy were inconclusive. Officials and family members are awaiting the results of blood-toxicology tests to learn whether there was something in his system that could have killed Rakes. Kelly said he expects to get at least some preliminary information by Wednesday.

The U.S. Attorney's Office in Boston declined to comment on Rakes' death today.